Chemically decomposable thermosetting resin composition for recycling fiber-reinforced composite and dissolving method thereof

Abstract

Disclosed is a chemically decomposable thermosetting resin composition for recycling a fiber-reinforced composite, including an epoxy resin, a multifunctional glycidyl-ester-based compound, an additive having a hydroxyl group on at least one of terminals of a main chain thereof, and an acid-anhydride-based curing agent, thus exhibiting excellent chemical decomposition performance in a basic solution and a high glass transition temperature. A method of dissolving the thermosetting resin composition is also provided. Thereby, a thermosetting composite material containing a thermosetting resin of the invention enables recycling of carbon fiber through hydrolysis, and thus the carbon fiber recycling industry and the recycled resin industry can be newly expanded. The thermosetting resin can be applied to fields using not only carbon composite materials but also general thermosetting resins, and can be hydrolyzed in a basic solution, which can significantly reduce landfill or disposal costs.

1 . A chemically decomposable thermosetting resin composition, comprising:
 an epoxy resin;   a multifunctional glycidyl-ester-based compound;   an additive having a hydroxyl group on at least one of terminals of a main chain thereof, the additive being at least one selected from the group consisting of compounds represented by Chemical Formulas 2 to 4 below; and   an acid-anhydride-based curing agent,   wherein the thermosetting resin composition comprises, based on 100 wt % of a total amount thereof excluding the curing agent, 1 to 98 wt % of the epoxy resin, 1 to 98 wt % of the multifunctional glycidyl-ester-based compound, and 1 to 30 wt % of the additive having a hydroxyl group on at least one of terminals of the main chain thereof:   
       
         
           
           
               
               
           
         
         (in Chemical Formula 2, 
         n is 0 or 1; 
         R 1  is hydrogen or a linear or branched C 1-5  alkyl; and 
         R 2 s are each independently 
       
       
         
           
           
               
               
           
         
       
       and the same as or different from each other, wherein u is 0 to 330, v is 0 to 430, both u and v are not zero, and repeating units 
       
         
           
           
               
               
           
         
       
       in parentheses are randomly arranged); 
       
         
           
           
               
               
           
         
         (in Chemical Formula 3, 
         R 3  is hydrogen, a linear or branched C 1-5  alkyl, cycloalkane having 5 to 10 atoms, benzene or naphthalene; 
         r is 1 to 6; 
         p is 0 to 430, q is 0 to 330, and both p and q are not zero; 
         repeating units 
       
       
         
           
           
               
               
           
         
       
       in parentheses are randomly arranged; and
 Chemical Formula 3 is configured such that R 3  is substituted with 
 
       
         
           
           
               
               
           
         
         (in Chemical Formula 4, 
         R 4  is a linear or branched C 1-5  alkyl, cycloalkane having 5 to 10 atoms, benzene or naphthalene; 
         s is 0 to 430; 
         t is 1 to 6; and 
         Chemical Formula 4 is configured such that R 4  is substituted with 
       
       
         
           
           
               
               
           
         
       
     
     
         2 . The chemically decomposable thermosetting resin composition of  claim 1 , wherein the multifunctional glycidyl-ester-based compound is at least one compound represented by Chemical Formula 1 below: 
       
         
           
           
               
               
           
         
         (in Chemical Formula 1, 
       
       
         
           
           
               
               
           
         
       
       is cycloalkane having 5 to 10 atoms, benzene or naphthalene;
 x is 1 to 5; and 
 y is 1 to 10). 
 
     
     
         3 . The chemically decomposable thermosetting resin composition of  claim 1 , wherein the acid-anhydride-based curing agent is contained in an amount of 70 to 160 parts by weight based on 100 parts by weight of a total amount of the epoxy resin, the multifunctional glycidyl-ester-based compound and the additive having a hydroxyl group on at least one of terminals of the main chain thereof. 
     
     
         4 . The chemically decomposable thermosetting resin composition of  claim 1 , wherein the acid-anhydride-based curing agent is at least one selected from the group consisting of phthalic anhydride (PA), succinic anhydride, maleic anhydride, methyl nadic anhydride (MNA), and methyl tetrahydrophthalic anhydride (MeTHPA). 
     
     
         5 . The chemically decomposable thermosetting resin composition of  claim 1 , wherein the additive having a hydroxyl group on at least one of terminals of the main chain thereof has a number average molecular weight of 150 to 20000 g/mol. 
     
     
         6 . A thermosetting composite material, comprising:
 the thermosetting resin composition of  claim 1 ; and   a carbon reinforcement.   
     
     
         7 . A method of manufacturing the thermosetting composite material of  claim 7 , comprising:
 mixing the thermosetting resin composition with a carbon reinforcement (step 1); and   curing the composition and the carbon reinforcement of step 1 (step 2).   
     
     
         8 . A method of dissolving a thermosetting resin, comprising dissolving a thermosetting resin composition from the thermosetting composite material of  claim 6  in a basic solution. 
     
     
         9 . The method of  claim 8 , wherein the basic solution further contains a salt including any one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). 
     
     
         10 . The method of  claim 8 , wherein a temperature of the basic solution is 50 to 120° C. 
     
     
         11 . A method of recovering a carbon reinforcement, comprising:
 dissolving a thermosetting resin from the thermosetting composite material of  claim 6  in a basic solution (step a); and   recovering the carbon reinforcement that is not dissolved in the basic solution (step b).